<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>后台管理系统</title>
</head>
<style>
    * {
        margin: 0;
        padding: 0;
        list-style: none;
    }
    .header{
        height: 80px;
        background-color: #333;
    }
    html,body,.container{
        height: 100%;
        /* 超出部分隐藏 */
        overflow: hidden;
    }
    .left{
        height: 100%;
        width: 200px;
        background-color: #ededee;
        float: left;
    }
    .right{
        height: 100%;
        /* 百分比减去固定值 */
        width: calc(100% - 200px);
        float: right;
        padding: 10px;
        box-sizing: border-box;
    }
    .content{
        height: 80%;
        width: 100%;    
        background-color: rosybrown;
        overflow: scroll;
    }
</style>
<body>
    <div class="container">
        <div class="header"></div>
        <div class="left"></div>
        <div class="right">
            <div class="content">
            <div style="height: 2000px;background-color: royalblue;">内容</div>
        </div>
        </div>
    </div>
</body>
</html>